Units of ESP cube file

[Nathan Keilbart]

Hello everyone,

I am working on computing values from the ESP cube file generated from the property module using the following input:

title nwchem

permanent_dir ./permanent

scratch_dir ./scratch

memory stack 2000 mb heap 100 mb global 800 mb

start nwchem

geometry units angstrom nocenter noautosym noautoz
  C  -0.64679100  -0.04226300   0.08434000
  N   0.82400400   0.05478200  -0.11510300
  O   1.32721400   1.18240400  -0.04647900
  O   1.43498500  -1.00181100  -0.31453000
  H  -1.01645300  -0.89457700  -0.48981600
  H  -0.81878000  -0.18192400   1.15320500
  H  -1.10417900   0.88338900  -0.27161700
end

basis noprint
  * library 6-31G**
end

dft
  direct
  grid fine
  xc B3LYP
  tolerances tight
  maxiter 500
  mult 1
end

driver
  default
  maxiter 150
  xyz geom
end

task dft optimize

basis noprint
  * library 6-311++G(2d,2p)
end

dft
  direct
  grid fine
  xc B3LYP
  tolerances tight
  maxiter 500
  mult 1
end

task dft energy

property
  esp
  grid rmin -6.0 -6.0 -5.0 rmax 6.0 6.0 6.0 ngrid 121 121 111 output esp.cube
end

task dft property

We are wanting to know in what units the cube file is written. We are attempting to compare our results with previously calculated results and need to convert it to kcal/mol. Please let us know if there is any other information we can provide.

Nathan

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Nathan Keilbart, PhD

Postdoctoral Research Scientist, Quantum Simulations Group

Lawrence Livermore National Laboratory

(925) 423-6620

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[Edoardo Aprà]

I have done a quick look at the source code and it seems that the units used to write the esp cube file are atomic units.